Research Disclosure

摘要

This research disclosure relates to a method and apparatus for improving a conversion efficiency of a radiation source. The radiation source may be an extreme ultraviolet (EUV) radiation source. The EUV radiation source may provide EUV radiation to an EUV lithographic apparatus. One method of generating EUV radiation involves directing a drive laser beam (e.g. a CO? laser beam) via a laser system towards droplets of fuel (e.g. tin) at a plasma formation location to create a plasma. The plasma then emits EUV radiation which is reflected by a radiation collector such that the EUV radiation is focused through an intermediate focus. The radiation collector includes an aperture through which the drive laser beam passes in order to be incident upon the plasma formation location. The intermediate focus may be situated at the entrance of an illuminator of a lithographic apparatus. A cone with protective vanes situated around its circumference provides an entrance to the intermediate focus. The EUV radiation source is contained within a vessel. The EUV radiation source may be referred to as a laser produced plasma (LPP) source.